@Oscamax i can see why have made your choices and at the costs you are incurring it would make little sense to install an additional battery. I think I will be seeking financial advice though if you can get savings account at 5% for 16 years 🤔
My Barclays Blue Rewards pays 5% for the first £5,000.
Unfortunately I have suffered a brain injury and occasionally I get confused and often say the wrong thing.